The Influence of Neodymium Element on the Crater Structure Formed on Al-17.5Si Alloy Surface Processed by High-Current Pulsed Electron Beam

Abstract

The effect of neodymium element on the elimination of crater structures on the surface of Al-17.5Si metallic materials processed by high-current pulsed electron beam was investigated in this study. Field emission scanning electron microscopy analysis indicated that the grain sizes of Al-17.5Si metallic materials were reduced and craters were removed from surfaces of the processed Al-17.5Si metallic material after addition of Nd. This can be attributed to the efficient transfer of heat accumulated in rich-silicon (primary silicon) areas without the eruption of a primary silicon phase if the size of primary silicon grains are small. The X-ray diffraction analysis indicates that all diffraction peaks are broadened because of the presence of structural defects, grain refinement and stress state. Electron probe micro-analyzer analysis demonstrated that Al and Nd were evenly distributed on the surface of the treated alloy, which could be attributed to the diffusion of the element. Transmission electron microscopy analysis showed that nano-Al and nano-Si cellular textures were generated during the treated process. The formation of these structures can be attributed to rapid heating and cooling effects by the treatment. Finally, electrochemical tests revealed that the corrosion current density of Al-17.5Si metallic materials (with Nd, 0.3 wt.%.) surface decreased by three orders of magnitude compared with that of the processed Al-17.5Si metallic material surfaces (without Nd). This can be attributed to the elimination of craters and grain refining.